IEC 61108-7:2024

IEC 61108-7 ®
Edition 1.0 2024-05
INTERNATIONAL
STANDARD
Maritime navigation and radiocommunication equipment and systems – Global
navigation satellite systems (GNSS) –
Part 7: Satellite based augmentation system (SBAS) L1 – Receiver equipment –
Performance standards, methods of testing and required test results

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IEC 61108-7 ®
Edition 1.0 2024-05
INTERNATIONAL
STANDARD
Maritime navigation and radiocommunication equipment and systems – Global

navigation satellite systems (GNSS) –

Part 7: Satellite based augmentation system (SBAS) L1 – Receiver equipment –

Performance standards, methods of testing and required test results

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.060.30; 33.060.20 ISBN 978-2-8322-8555-8

– 2 – IEC 61108-7:2024 © IEC 2024
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 9
2 Normative references . 9
3 Terms, definitions and abbreviated terms . 10
3.1 Terms and definitions . 10
3.2 Abbreviated terms . 11
4 Minimum GNSS and SBAS performance standard . 13
4.1 General . 13
4.2 SBAS L1 receiver equipment . 13
4.2.1 Minimum facilities . 13
4.2.2 Configuration . 14
4.2.3 Quality assurance . 14
4.3 Performance standards for SBAS L1 receiver equipment . 14
4.3.1 General . 14
4.3.2 Equipment output . 14
4.3.3 Accuracy . 16
4.3.4 Acquisition . 17
4.3.5 Availability . 17
4.3.6 Dynamic range . 17
4.3.7 Effects of specific interfering signals . 17
4.3.8 Position update . 18
4.3.9 SBAS input and processing . 18
4.3.10 Navigational status indications . 19
4.3.11 Operation under typical interference conditions . 23
4.3.12 Output of COG, SOG and UTC . 23
5 SBAS technical characteristics . 24
5.1 General . 24
5.2 SBAS L1 SIS RF characteristics . 25
5.3 SBAS L1 SIS message characteristics . 25
5.3.1 Identification . 25
5.3.2 L1 C/A PRN Code for SBAS . 26
5.3.3 SBAS data format . 27
6 Methods of testing and required test results . 28
6.1 Test sites . 28
6.2 Test sequence . 29
6.3 Test signals . 29
6.4 Determination of accuracy . 30
6.5 Environmental conditions . 31
6.6 General requirements . 31
6.7 Alert requirements . 31
6.8 Presentation requirements . 31
6.9 Performance check . 31
6.10 SBAS L1 receiver tests descriptions . 32
6.10.1 SBAS L1 receiver equipment . 32
6.10.2 Configuration . 32

6.10.3 Position output. 32
6.10.4 Equipment output . 32
6.10.5 Static accuracy and availability . 32
6.10.6 Static accuracy with angular movement of the antenna . 33
6.10.7 Dynamic accuracy . 33
6.10.8 Acquisition . 33
6.10.9 Sensitivity and dynamic range . 34
6.10.10 Effects on specific interfering signals . 34
6.10.11 Position update . 34
6.10.12 SBAS input and processing . 35
6.10.13 SBAS message processing . 35
6.10.14 SBAS GEO satellite selection and switching . 38
6.10.15 Navigational status indications . 39
6.10.16 Test for typical interference conditions. 41
6.10.17 Accuracy of COG and SOG. 43
6.10.18 Validity of COG and SOG information . 44
6.10.19 Output of UTC . 44
6.10.20 Validation material for tropospheric model . 44
Annex A (normative) High level procedure for SBAS navigation computation . 45
A.1 GPS L1 signal processing . 45
A.2 SBAS L1 signal processing . 45
A.3 Application of SBAS messages . 45
A.4 SBAS position computation . 47
A.4.1 General . 47
A.4.2 Weighted least squares algorithm . 47
A.4.3 SBAS-based standard residual error . 48
Annex B (normative) Sentences to support SBAS L1 receiver operation . 49
B.1 General . 49
B.2 80GBS – GNSS satellite fault detection . 49
B.3 GFA – GNSS Fix Accuracy and Integrity . 51
B.4 GNS – GNSS fix data . 52
B.5 GRS – GNSS Range residuals . 58
B.6 GSA – GNSS DOP and active satellites . 61
B.7 GSN – GNSS SBAS navigation message . 65
B.8 GSV – GNSS Satellites in View . 66
B.9 RMC – Recommended minimum specific GNSS data . 69
B.10 VTG – Course over ground and ground speed . 71
Annex C (informative) GNSS interference, jamming and spoofing . 72
C.1 General . 72
C.2 Interference . 72
C.3 Jamming . 72
C.4 Spoofing . 73
Annex D (normative) Alert management . 74
Bibliography . 75

Table 1 – Output sentences defined for positioning purposes . 15
Table 2 – Output sentences for integration in other navigational aids . 16

– 4 – IEC 61108-7:2024 © IEC 2024
Table 3 – Required horizontal position accuracy and integrity for general navigation . 19
Table 4 – Accuracy of COG . 24
Table 5 – SBAS L1 SIS RF characteristics . 25
Table 6 – SBAS Ranging C/A Codes . 26
Table 7 – SBAS message format . 27
Table 8 – SBAS Message Types . 28
Table 9 – Broad-band interference . 42
Table 10 – Pulsed interference . 42
Table 11 – Continuous wave interference . 42
Table 12 – Broad-band interference . 43
Table D.1 – Required alerts and their classification. 74

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MARITIME NAVIGATION AND RADIOCOMMUNICATION EQUIPMENT AND
SYSTEMS – GLOBAL NAVIGATION SATELLITE SYSTEMS (GNSS) –

Part 7: Satellite based augmentation system (SBAS) L1 –
Receiver equipment – Performance standards,
methods of testing and required test results

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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9) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
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the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC 61108-7 has been prepared by IEC technical committee 80: Maritime navigation and
radiocommunication equipment and systems. It is an International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
80/1104/FDIS 80/1114A/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
– 6 – IEC 61108-7:2024 © IEC 2024
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all parts in the IEC 61108 series, published under the general title Maritime navigation
and radiocommunication equipment and systems – Global navigation satellite systems (GNSS),
can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
INTRODUCTION
Satellite based augmentation system (SBAS) is designed to augment Global Navigation
Satellite System (GNSS) by broadcasting additional signals from geostationary (GEO)
satellites. The basic scheme is to use a set of ground monitoring stations (at precisely surveyed
locations) to receive GNSS signals that are processed and transmitted to the master station(s)
which formulates the correction messages applicable to users within the service area (i.e.
ionospheric errors, satellite position/clock errors, etc.). These corrections are then transmitted
to navigation payloads via uplink stations on GEO satellites. The GEO satellites then transmit
these corrections in a GNSS-like signal across the service area. An integrity message is also
broadcasted enabling receivers to remove errors in the GNSS signal for increased position
accuracy and integrity. Users are notified within a few seconds of information that could lead to
position error.
SBAS are civil aviation safety-critical system and are designed according to an international
standard (SARPs:2023). So far, SBAS have already been commissioned by the US (Wide Area
Augmentation System – WAAS), Europe (European Geostationary Navigation Overlay Service
– EGNOS), Japan (Michibiki Satellite Augmentation System – MSAS) and India (GPS Aided
GEO Augmented Navigation – GAGAN). At September 2022, analogous systems are under
commissioning or development in other regions of the world such as BeiDou Satellite Based
Augmentation System – BDSBAS in China, System of Differential Correction and Monitoring –
SDCM in Russia, Korea Augmentation Satellite System – KASS in Republic of Korea, Southern
Positioning Augmentation System – SouthPAN in Australia and New Zealand, Augmented
Navigation for Africa – ANGA and the Solución de Aumentación para Caribe, Centro y
Sudamérica – SACCSA in South/Central America and the Caribbean.
The maritime community is interested in using SBAS for ocean waters, coastal waters and
harbour entrances/approaches in order to fulfil the agreed international operational
performance requirements (IMO Resolution A.1046(27)), especially where there is no other
augmentation service available (i.e. DGPS/DGLONASS) or in poorly covered environments.
Besides, when Ground Based Augmentation Systems (GBAS) are available, SBAS could
become either the primary augmentation system or could act as a back-up. SBAS aims at
providing satellite clock/ephemeris corrections, ionospheric corrections and integrity
information to GNSS signals that meet maritime requirements, enhanced accuracy and integrity
information.
IMO MSC.401(95) and IEC 61108-4 (Shipborne DGPS and DGLONASS maritime radio beacon
receiver equipment) allow the use of different augmentation signals in shipborne receivers but
there is neither an IMO or IEC standard on how to process and implement SBAS signals in
shipborne receivers. One of the operational and functional requirements (Module B) of IMO
Resolution MSC.401(95) is that the equipment has the facilities to process augmentation data
in accordance with the appropriate methods, e.g. Recommendation ITU-R M.823, RTCM 10410,
or other relevant standards, already existing or still to be developed in particular for satellite
based augmentation system (SBAS) adoption. This document provides the requested standard
for SBAS L1 augmenting GPS L1.
Most of recent maritime GNSS receiver models are SBAS compatible but present important
differences in their performance since they are not certified according to any specific test
standard.
IEC 61108 is a series of IEC standards for "Maritime navigation and radio-communication
equipment and systems – Global navigation satellite systems (GNSS)". IEC has published
International Standards for the following GNSS systems: IEC 61108-1 for GPS, IEC 61108-2
for GLONASS, IEC 61108-3 for Galileo, IEC 61108-5 for BDS and IEC 61108-6 for IRNSS. In
addition, IEC has published International Standard IEC 61108-4 for DGPS and DGLONASS
which are Differential Global Navigation Satellite System (DGNSS) enhancing the primary
GNSS constellations (GPS and GLONASS).

– 8 – IEC 61108-7:2024 © IEC 2024
This document includes the minimum performances for the shipborne receivers, using SBAS
L1 signals augmenting GPS L1, in order to be compliant with the IMO Resolution A.1046(27)
operational requirements for ocean waters, harbour entrances, harbour approaches and coastal
waters, along with the methods of testing and required test results.
Satellite Based Augmentation Systems (SBAS) are available in several regions worldwide to
augment GPS L1 frequency by broadcasting additional SBAS L1 signals:
• SBAS are designed according to the same international standard (SARPs:2023).
• GPS L1 signal specification is presented in the GPS Interference Specification
(IS-GPS-200).
A description of the GPS Standard Positioning Service Performance Standard (GPS-SPS-PS)
is available at https://www.gps.gov.
NOTE A standard including dual-frequency multi-constellation (DFMC) SBAS services will be considered when
appropriate.
MARITIME NAVIGATION AND RADIOCOMMUNICATION EQUIPMENT AND
SYSTEMS – GLOBAL NAVIGATION SATELLITE SYSTEMS (GNSS) –

Part 7: Satellite based augmentation system (SBAS) L1 –
Receiver equipment – Performance standards,
methods of testing and required test results

1 Scope
This part of IEC 61108 specifies the minimum performance standards, methods of testing and
required test results for Satellite based augmentation system (SBAS) shipborne receiver
equipment, which uses L1 signals from GPS and satellite based augmentation system (SBAS)
in order to improve the estimated GPS position.
This document addresses the use of SBAS L1 to provide augmentation to the GPS shipborne
receiver (IMO Resolution MSC.112(73)). This document includes the minimum performances
for SBAS L1 maritime receivers to be obtained by the receiver equipment under coverage of
SBAS service in order to be compliant with the IMO Resolution A.1046(27) describing
operational requirements for ocean waters, harbour entrances, harbour approaches and coastal
waters.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60721-3-6:1987, Classification of environmental conditions – Part 3: Classification of
groups of environmental parameters and their severities – Ship environment
IEC 60945, Maritime navigation and radiocommunication equipment and systems – General
requirements – Methods of testing and required test results
IEC 61108-1:2003, Maritime navigation and radiocommunication equipment and systems –
Global navigation satellite systems (GNSS) – Part 1: Global positioning system (GPS) –
Receiver equipment – Performance standards, methods of testing and required test results
IEC 61162-1, Maritime navigation and radiocommunication equipment and systems – Digital
interfaces – Part 1: Single talker and multiple listeners
IEC 61162-2, Maritime navigation and radiocommunication equipment and systems – Digital
interfaces – Part 2: Single talker and multiple listeners, high-speed transmission
IEC 61162-450, Maritime navigation and radiocommunication equipment and systems – Digital
interfaces – Part 450: Multiple talkers and multiple listeners – Ethernet interconnection
IEC 62923-1, Maritime navigation and radiocommunication equipment and systems – Bridge
alert management – Part 1: Operational and performance requirements, methods of testing and
required test results
IEC 62923-2, Maritime navigation and radiocommunication equipment and systems – Bridge
alert management – Part 2: Alert and cluster identifiers and other additional features

– 10 – IEC 61108-7:2024 © IEC 2024
IEC 62288, Maritime navigation and radiocommunication equipment and systems –
Presentation of navigation-related information on shipborne navigational displays – General
requirements, methods of testing and required test results
RTCA DO-229F:2020, Minimum Operational Performance Standards (MOPS) for Global
Positioning System/Satellite-Based Augmentation System Airborne Equipment.
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1.1
accuracy
degree of conformance between the estimated or measured parameter of a craft at a given time
and its true parameter at that time
Note 1 to entry: Parameters in this context may be position coordinates, velocity, time, angle, etc.
Note 2 to entry: In particular, relative accuracy is the accuracy with which a user can determine position relative to
that of another user of the same navigation system at the same time.
[SOURCE: IMO Resolution A.915(22)]
3.1.2
augmentation
any technique of providing enhancement to the GNSS in order to provide improved navigation
performance to the user
Note 1 to entry: Satellite based augmentation system (SBAS) is a system providing additional satellite signals in
order to enhance the performance of the GNSS service.
Note 2 to entry: Differential Global Navigation Satellite System (DGNSS) is a system providing additional signals
from a ground-based station in order to enhance the performance of the GNSS service.
[SOURCE: IMO Resolution A.915(22)]
3.1.3
availability
percentage of time that an aid, or system of aids, is performing a required function under stated
conditions. The non-availability can be caused by scheduled and/or unscheduled interruptions
Note 1 to entry: Signal availability is the availability of a radio signal in a specified coverage area.
Note 2 to entry: System availability is the availability of a system to a user, including signal availability and the
performance of the user's receiver.
[SOURCE: IMO Resolution A.915(22)]
3.1.4
horizontal alert limit
HAL
maximum allowable horizontal error in the measured position – during integrity monitoring –
before an alert is triggered
3.1.5
horizontal accuracy 95 %
95 percentile of the Horizontal Position Error (HPE) distribution, where HPE is the 2D radial
error of the instantaneous measured position with respect to the true instantaneous position
Note 1 to entry: This definition corresponds with position error (percentile 95 %) within the document.
3.1.6
horizontal protection level
HPL
radius of a circle in the horizontal plane with its centre being at the true position, which specifies
the region assured to contain the indicated horizontal position
Note 1 to entry: It is the horizontal region for which the missed alert requirement can be met.
3.1.7
integrity
ability to provide users with warnings within a specified time when the system should not be
used for navigation and the horizontal accuracy is not within the selected accuracy level
specified in 4.3.10.1
3.1.8
integrity monitoring
process of determining whether the system performance (or individual observations) allow use
for navigation purposes.
Note 1 to entry: Overall GNSS system integrity is described by three parameters: the threshold value or alert limit,
the time to alarm and the integrity risk.
Note 2 to entry: The output of integrity monitoring is that individual (erroneous) observations or the overall GNSS
system cannot be used for navigation.
Note 3 to entry: Integrity risk is the probability that a user will experience a position error larger than the threshold
value without an alarm being raised within the specified time to alarm at any instant of time at any location in the
coverage area.
3.1.9
SBAS position
position computed by a GNSS shipborne receiver equipment using GNSS satellite
constellation(s) augmented by SBAS
3.1.10
SBAS L1 receiver equipment
all the components and units necessary for the system to properly perform its intended
functions, which includes the use case when a shipborne receiver provides a position using
GPS satellite constellation augmented by SBAS L1
Note 1 to entry: When the same GNSS shipborne receiver equipment provides a PVT solution not augmented, this
document is not applicable.
3.2 Abbreviated terms
BAM bridge alert management
BDS BeiDou navigation satellite system
C/A coarse/acquisition
COG course over ground
DGPS differential GPS
EGNOS European Geostationary Navigation Overlay Service
EUT equipment under test
Galileo European global navigation satellite system

– 12 – IEC 61108-7:2024 © IEC 2024
GBAS ground based augmentation systems
GEO GEOstationary satellite
GIVEI grid ionospheric vertical error indicator
GNSS global navigation satellite system
GLONASS Global'naya Navigatsionnaya Sputnikovaya Sistema
GPS global positioning system
HDOP horizontal dilution of precision
ICAO International Civil Aviation Organization
ICD interface control document
IGP ionospheric grid point
IMO International Maritime Organization
IODF issue of data fast corrections
IODI issue of data IGP mask
IODP issue of data PRN mask
ITU-R International Telecommunication Union-Radiocommunication
L1 GPS frequency 1 575,42 MHz
MKD minimum keyboard and display
MT message type
NavIC(IRNSS) Navigation with Indian constellation
PDOP position dilution of precision
PNT position, navigation and timing
PRN pseudo random noise
PVT position velocity time
QZSS Quasi-Zenith satellite system
RAIM receiver autonomous integrity monitoring
RF radio frequency
RTCA Radio Technical Commission for Aeronautics
RTCM Radio Technical Commission for Maritime Services
SBAS satellite based augmentation system
SIS signal in space
SNR signal-to-noise ratio
SOG speed over ground
SPS standard positioning service
UDRE user differential range error
UDREI user differential range error indicator
UTC coordinated universal time

4 Minimum GNSS and SBAS performance standard
4.1 General
This document contains the basic minimum performance standard of SBAS L1 receiver
equipment for navigational PVT solution.
SBAS is designed to provide satellite clock, ephemeris and ionospheric corrections and integrity
information to the GNSS signals, obtaining enhanced accuracy and integrity information. This
document covers the SBAS L1 services augmenting GPS L1 signals.
NOTE 1 SBAS is referenced as an augmentation system in MSC.401(95) and its amendment MSC.432(98).
The SBAS L1 receiver equipment shall comply with GPS receiver equipment IEC 61108-1
operating on the L1 signal and C/A code.
NOTE 2 IEC 61108-1 covers the basic requirements of position fixing for navigation purposes only and does not
cover other computational facilities which can be provided in the equipment. Other computational activity,
input/output activity or extra display functions if provided do not degrade the performance of the equipment below
the minimum required performance.
NOTE 3 An SBAS L1 receiver equipment operating without SBAS augmentation is able to provide standard PVT
solution for a GNSS system.
4.2 SBAS L1 receiver equipment
(See 6.10.1)
4.2.1 Minimum facilities
The SBAS L1 receiver equipment shall include the following minimum facilities:
a) antenna capable of receiving GPS L1 and SBAS L1 signals;
b) receiver and processor capable of processing GPS L1 and SBAS L1 signals to support
SBAS position;
c) means of accessing the computed PVT information;
d) data control and interface;
e) position display and, if required, other forms of output;
f) SBAS indicator when SBAS augmentation is applied in the PVT solution;
g) receiver correlator and front-end characteristics (i.e. 3dB pre-correlation bandwidth,
average correlator spacing, instantaneous correlator spacing and equipment differential
group delay) as specified in RTCA DO-229F:2020, 2.1.4.5.1; and
h) alert management.
If SBAS forms part of an approved Integrated Navigation System (INS), requirements of
facilities c) d) e), f) and h) may be provided within the INS.
If SBAS forms part of an approved multi-system PNT, requirements of facilities c) d) e) and f)
may be provided within the multi-system PNT.

– 14 – IEC 61108-7:2024 © IEC 2024
4.2.2 Configuration
(See 6.10.2)
The SBAS L1 receiver equipment shall provide the facility for the user to enable or disable the
SBAS usage to compute the PVT solution.
Besides the automatic capability of the SBAS tracking signals, it is recommended that the SBAS
L1 receiver equipment allows the user to manually configure the service provider to be used.
NOTE This optional capability is specifically useful in overlapping areas.
In addition, the following configuration shall be available in the SBAS L1 receiver equipment:
a) automatic mode: When DGPS and SBAS L1 augmentation signals are both available in the
receiver, SBAS L1 receiver equipment shall prioritize the use of DGPS corrections over
SBAS L1 to compute the PVT solution (DGPS>SBAS).
b) manual mode: SBAS L1 receiver equipment shall provide the facility for the user to select
the preferable augmentation signal to be used in the PVT solution, including as options at
least DGPS and SBAS L1.
4.2.3 Quality assurance
The equipment shall be designed, produced and documented by manufacturers complying with
approved quality systems as applicable.
4.3 Performance standards for SBAS L1 receiver equipment
4.3.1 General
The SBAS L1 receiver equipment shall operate on the GPS L1 C/A signal meeting the
requirements of IEC 61108-1.
The SBAS L1 receiver equipment shall operate on the SBAS L1 signal as specified in this
document.
The equipment shall have the facilities to process SBAS augmentation data in accordance with
the procedure shown in Annex A.
4.3.2 Equipment output
(See 6.10.3 and 6.10.4)
The SBAS L1 receiver equipment shall provide latitude and longitude position information in
degrees, minutes and thousandths of minutes referenced to the World Geodetic System (WGS-
84) coordinate system, as well as provide time referenced to Coordinated Universal Time (UTC).
The SBAS L1 receiver equipment shall be provided with at least two outputs from which position
information can be supplied to other equipment. The physical interface shall be based on
IEC 61162-1 or IEC 61162-2 or IEC 61162-450.
When SBAS information is used for positioning reporting purposes, the sentences in Table 1
shall be available in any combination. When SBAS information is not used, the sentences listed
in Table 1 shall operate as specified in related equipment standards for operation without SBAS.

Table 1 – Output sentences defined for positioning purposes
Mnemonic Description Considerations for SBAS navigation position
b
GNSS satellite fault detection If SBAS satellites are used for ranging in
GBS
navigation position:
SBAS satellite ID: The offset from SBAS SV ID
to SBAS PRN number is 87.
b
GNSS fix data If SBAS information is used for navigation
GNS
position:
Navigational status indicator: S, C, U or V,
corresponding to Safe, Caution, Unsafe or
Navigational status not valid
Mode indicator: D (multiple characters). D refers
to Differential, Satellite system used in
differential mode in position fix
Age of differential data: For SBAS L1, this value
is the oldest age of the most recent fast
corrections set in use (received through
messages types 2, 3, 4, 5 and 24).
Differential source ID: PRN of the SBAS service
preceded by 1 (e.g. 1126 for PRN 126).
HDOP: Calculated HDOP.
b
Recommended Minimum Specific GNSS If SBAS information is used for navigation
RMC
Data position:
Navigational status: S, C, U or V, corresponding
to Safe, Caution, Unsafe or Navigational status
not valid
Mode indicator: D (single character), indicating
differential.
Status: A, indicating data valid
b
Course over ground and ground speed If SBAS information is used for navigation
VTG
position:
Mode indicator: D (single character), indicating
differential.
a
Time and date No specific consideration for SBAS navigation
ZDA
position
b
GNSS fix accuracy and integrity If integrity is provided by RAIM using corrections
GFA
and integrity data provided by SBAS:
Integrity status: S, C, U or V, corresponding to
Safe, Caution, Unsafe or Integrity status not
valid for the first character (RAIM) and the
second character (SBAS).
b
GNSS SBAS Navigation Message If SBAS information is used for navigation
GSN
position.
a
IEC 61162-1 applies.
b
Annex B applies.
In addition, for integrating with other navigational aids the sentences in Table 2 may be
available in any combination.
– 16 – IEC 61108-7:2024 © IEC 2024
Table 2 – Output sentences for integration in other navigational aids
Mnemonic Description Considerations for SBAS navigation position
b
GNSS range residuals If SBAS satellites are used for ranging in
GRS
navigation position:
SBAS signal ID: The offset from SBAS SV ID to
SBAS PRN number is 87.
b
GNSS DOP and active satellites If SBAS satellites are used for ranging in
GSA
navigation position:
SBAS satellite ID: The offset from SBAS SV ID
to SBAS PRN number is 87.
a
If SBAS information is used for navigation
GNSS pseudorange noise statistics
GST
position:
Position error estimation after SBAS corrections
application.
RMS of the pseudorange after SBAS corrections
application.
b
GNSS satellites in view If SBAS satellites are in view:
GSV
SBAS satellite ID: The offset from SBAS SV ID
to SBAS PRN number is 87.
a
See IEC 61162-1.
b
See Annex B.
The following sentences shall be used for alert reporting and alert command purposes where
required by IEC 62923-1:
• ACN – Alert command
• ALC – Cyclic alert list
• ALF – Alert sentence
• ARC – Alert command refused
• HBT – Heartbeat supervision sentence
4.3.3 Accuracy
4.3.3.1 Static accuracy
(See 6.10.5 and 6.10.6)
The SBAS L1 receiver equipment shall be capable of achieving such static accuracy that the
horizontal position of the antenna is determined to within 10 m (percentile 95 %) with HDOP ≤4
(or PDOP ≤ 6).
NOTE 1 This minimum accuracy requirement is compliant with the IMO Resolution A.1046(27) operational
requirements for ocean waters, harbour entrances, harbour approaches and coastal waters.
NOTE 2 See hori
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